Fixed a bug in the Slack installer code.

linux-game-manager.sh

@@ -518,9 +518,7 @@ case "${game}" in
             if command -v yay &> /dev/null ; then
                 yay -Sy --noconfirm --sudoloop freedoom gzdoom
             elif command -v slapt-get &> /dev/null ; then
-                su
-                slapt-get -i freedoom gzdoom
-                exit
+                su -c slapt-get -i freedoom gzdoom
             else
                 dialog --backtitle "Linux Game Manager" --msgbox "No supported package managers found. Please install the freedoom and gzdoom packages manually." -1 -1
                 exit 0